The National Flag of Switzerland is square. The Swiss Naval Ensign was
adopted with the proportions 2:3. Nick Artimovich, 12 February 1996

The Swiss flag has been used in an unofficially rectangular shape during
opening ceremonies and throughout the games in several Olympic Games,
this is documented from probably most - if not all - of the Olympic
Games. The same applies to other international sports or non governmental
events. I say "unofficially", because the official proportion is 1:1, as
every vexillologist knows, except for the national flag for use on sea,
which is rectangular with proportions 2:3. But then, no national flags at
sea are used during ceremonies at Olympic Games.

As a matter of
fact, nobody within the Swiss government cares about the size of our
national flag during Olympic Games, which are a joyful and peaceful event of
humankind. It just complies with the local rules and does what everybody
does, thus keeping problems away. There are no official directions as to
how the Swiss flag should look during events outside the country. Most
Swiss flags used at such events are not manufactured in Switzerland
anyway.

If the issue is not sports and world-wide joy, but politics,
then the Swiss flag is kept square, like outside the U.N. headquarters in
New York and Geneva. Nepal and Switzerland are the only countries within
the United Nations not showing the standard rectangular 2:3 flag but the
original proportions.

As everybody knows, the standardization of flag
proportions during big events follows economic and practical reasons:
ordering 10000 flags of the same size is cheaper than ordering 200 sets
of 50 flags, with many sets of different sizes. The even more important
reason is to avoid the negative public impact of one country being
bigger, i.e. different, than the other. At Olympic Games "everybody is
equal", and "vexillology, what the hell is that?".

There's no great
use to discuss about sizes, but we can learn from such a problem to tell
good flag design = high identification value, from bad flag design. Good
flags remain good, whatever its shape may be.

In the 1980 Moscow Olympics, Switzerland (and a few other nations)
marched under the Olympic flag in partial support of the US-led boycott
protesting the Soviet invasion of Afghanistan. In recent Olympics, the 1992
Barcelona games are the only instance I find of the Swiss marching behind a
square flag in the opening ceremonies. All summer games since then have featured
a rectangular flag. Ditto for all winter games 1988, 1998 and following. Clips
in youtube are the evidence.

So, in what other games did Switzerland
carry a square flag? Barring any specific evidence, and despite the record of
recent games, I would still expect the more correct square flag to be the
predominant usage in earlier games. Note that the flag leading a national
delegation is one of a kind, and not subject to the strictures of mass
production. The flags raised at medal ceremonies at various venues are another
matter, and more logically subject to pressures for uniformity in proportions.